The familial magnesium-losing kidney.

Magnesium deficiency is often secondary to existing disease. Over a period of 20 years, 17 cases of primary magnesium-losing kidney have been reported. This report describes two additional cases, and a comparison with previous cases is made. The familial magnesium-losing kidney appears to be caused by a congenital tubular defect in the reabsorption of magnesium. Its manifestations may be various but the diagnosis is established by the presence of hypomagnesemia with an unappropriately high urinary magnesium excretion in patients with no other renal disorder.